I don't underestimate the effort required to create a puzzle of this sort, but these increasingly seem to be dashed off, and are less of a challenge to the solver than before. In this case, four of the unclued lights have two possible solutions (per Chambers). In the final analysis, it's unimportant, I suppose, because there is no ambiguity about the crossing answers, but it seems sloppy, as if not properly checked before publication. Strictly speaking, the preamble is correct, but it could perhaps have been flagged that unclued lights had multiple answers and that either would be acceptable solutions.